Interstate 90 | |
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Route information | |
Defined by SDCL §31-4-184 | |
Maintained by SDDOT | |
Length: | 412.76 mi (664.27 km) |
Major junctions | |
West end: | I-90 / US 14 at Wyoming state line |
I-190 / US 16 in Rapid City I-29 in Sioux Falls I-229 in Sioux Falls |
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East end: | I-90 at Minnesota state line |
Highway system | |
In the U.S. state of South Dakota, Interstate 90 traverses east–west through the southern half of the state.
Interstate 90 enters South Dakota in Lawrence County as a four-lane divided highway. It enters concurrently with U.S. Route 14, and passes through the town of Spearfish, where it shares another concurrency with U.S. Route 85 from exit 10 to exit 17. From there it passes several miles north and east of the tourist town of Deadwood before entering Meade County, going just to the west of Sturgis. Another concurrency is with South Dakota Highway 34 from exit 23 at Whitewood to exit 30, the west exit of Sturgis, where there starts a concurrency with SD 79. The freeway generally passes along the north and east edges of the Black Hills.
The route then enters Pennington County, where it passes through the northern edge of Rapid City, gateway to the Black Hills and the nearest passing to Mount Rushmore National Memorial, as well as other scenic attractions including Custer State Park and the Needles Highway. Rapid City is also where the interstate has its westernmost auxiliary route, Interstate 190, which links the interstate to the western edge of the downtown area. SD 79's concurrency ends at exit 61 on the east side of the city. From Rapid City, the route heads east, passing between Box Elder to the south and Ellsworth Air Force Base to the north before heading towards Wall on to Jackson County. Exits 110 and 131 for Badlands National Park to the south (SD 240) are within 15 miles (24 km) either way of the county line. The concurrency for US-14 ends at exit 112 just east of Wall; here US-14 runs due east and will connect to the city of Philip and the capital city of Pierre.